STUDY DESIGN: Resident's Case StudyBACKGROUND/INTRODUCTION: The reports of spinal accessory nerve injury in the literature primarily focus on injury following surgical dissection or traumatic stretch injury. There is limited literature describing the presentation and diagnosis of this injury with an unknown cause. The purpose of this case report is to describe the clinical decision-making process that guided the diagnosis and treatment of a complex patient with spinal accessory nerve palsy (SANP) whose clinical presentation and response to therapy were inconsistent with the results of multiple diagnostic tests.CASE DESCRIPTION: The patient was a 27-year-old female triathlete with a five month history of right-sided neck, anterior shoulder, and chest pain.OUTCOME: Based on the physical exam, magnetic resonance imaging, radiographs, electrodiagnostic and nerve conduction testing, the patient was diagnosed by her physician with right sterno-clavicular joint strain and scapular dyskinesis and was referred to physical therapy. Care was initiated based on this initial diagnosis. Upon further examination and perusal of the literature, the physical therapist proposed a diagnosis of spinal accessory nerve injury. Intervention included manual release of soft tissue tightness, neuromuscular facilitation and sport-specific strengthening, resulting in full return to functional and sport activities. These interventions focused on neurological re-education and muscular facilitation to address SANP as opposed to a joint sprain and dysfunction, as initially diagnosed.DISCUSSION: Proper diagnosis is imperative to effective treatment in all patients. This case illustrates the importance of a thorough examination and consideration of multiple diagnostic findings, particularly when EMG/NCV tests were negative, the cause was not apparent, and symptoms were less severe than other cases documented in the literature.LEVEL OF EVIDENCE: Diagnosis, level 4.